Fresnel lens solar fluid heater

ABSTRACT

A continuous-flow fluid heater using solar energy is presented, where the solar heating is accomplished by means of a Fresnel lens focused on a conduit through which fluid is conveyed at a rate sufficient to heat the fluid to a desired temperature. The Fresnel lens is pointed at the sun and the sun is tracked by means of an off-the-shelf clock drive or step-motor system. The fluids that can be heated include water and cooking oil, and with modifications to the system, other liquids including liquid metals.

FIELD OF THE INVENTION

The present invention relates to a solar energy collector and concentrator that converts solar energy into heat energy, based on a Fresnel lens.

BACKGROUND OF THE INVENTION

Solar energy converters that convert sunlight into heat energy typically employ parabolic mirrors or lenses to concentrate sunlight into a narrow beam at the focal point of the mirror or lens. The heat energy generated is a function of both the size or surface area of the mirror or lens and the intensity of the sunlight, based upon atmospheric considerations and the position of the sun in the sky.

Photovoltaic cells are the most expensive method of converting sunlight into useable energy. There are methods of using mirrors and lenses to concentrate sunlight to increase photovoltaic efficiency, such as U.S. Pat. Nos. 6,020,554 and 6,399,874 which utilize a Fresnel lens (a lens having a stepped or grooved surface), with or without combination with reflectors adjacent to the photovoltaic cell. Tracking mechanisms have been patented that adjust the orientation of the solar energy converter to meet the sun as it travels across the sky, improving efficiency.

Solar heaters using lenses and mirrors are less advanced, because they do not generate electric current directly. Lens-based solar heaters are not available that are low-cost, highly efficient, and can heat continuous fluid flows. The useable energy from such a system consists of hot water or other fluids that in turn can be used to heat buildings, cook food, and the like. This direct conversion from sunlight to heat energy bypasses the expense and inefficiency of using photovoltaic cells to generate electricity and then using the generated electricity to heat water.

Although it is not part of the present invention, it is expected that the heated fluid flows would be conducted to useful destinations when they reach a preset temperature by means of exposing them to the focused rays of the sun by the present invention. Typically, the uses for such heated fluids would be heated water for home use, heated swimming pools, laundromats, and the like. Cooking oil could also be heated with the present invention.

SUMMARY OF THE INVENTION

The essential features of the present invention are a plastic or glass Fresnel lens, a rotatable, adjustable mount that can be driven by a clock drive to keep it pointed at the sun to be used as a solar energy collector for the purposes of heating water or other fluids.

It is a related object of the invention to provide a solar energy heater that utilizes a single Fresnel lens as its sole heat source.

It is a further object of the invention to provide a programmable clock drive that can be set up based upon time of day and longitude and latitude to optimize the solar energy reception of the Fresnel lens heater.

It is a further object of this invention to provide a fluid heating system that can be located remotely from the reservoir of fluid to be heated and connected via a conduit,

It is a further object of the invention that a continuous fluid flow be presented to the concentrated solar radiation collected by the heater such that the flow is continuously heated to a predetermined temperature.

The objects of the present invention will become more apparent upon reference to the following detailed description and drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1. Perspective view of the invention

FIG. 2. Front view of the invention

FIG. 3. Close-up view of the heat transfer conduit alternate embodiment

FIG. 4. Cross-section of the heat transfer conduit alternate embodiment

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1 and FIG. 2, the solar fluid heater 100 is composed of a base 101, a pedestal 102, a support platform 103, a solar tracker controller 104, a ring gear 105, a lens support frame 106, a Fresnel lens 107, a plurality of solar tracking sensors 108, an azimuth positioning motor 109, an altitude positioning motor 110, a heat transfer conduit 111, a vertical support 112, a fluid transfer input 115, and a fluid transfer output 116.

The support platform 103 is supported by the cylindrical pedestal 102, which rests fixedly on the base 101. The support platform is rotated around the pedestal by means of the azimuth positioning motor 109, which engages the ring gear 105 lining the outside of the support base.

The vertical support 12 rests fixedly on the support platform 103 and serves as a support for the lens support frame 106 by means of two rotatable connection pivots at each side of the vertical support. The frame can be positioned altitudinally by means of the altitude positioning motor 109 attached to one side of the vertical support 112.

The solar tracker controller 104 accepts electronic input from the solar tracking sensors 108 as to the strength of the sun's rays and issues electronic commands to the azimuth positioning motor 109 and the altitude positioning motor 110 to adjust the position of the lens support frame 106 to maximize the exposure of the Fresnel lens 107 to the direct rays of the sun. In the preferred embodiment of the present invention, the solar tracker controller 104 is preprogrammed to follow the sun across the sky by means of commonly available algorithms used to control solar collection devices.

The Fresnel lens 107 is made from plastic or glass and is sized and focused to generate the desired intensity of solar radiation on the heat transfer conduit 111 such that the fluid flowing through the conduit by means of the fluid transfer input 115 and the fluid transfer output 116 is heated to the desired temperature.

The fluids that can be heated by the present invention in the preferred embodiment are water and cooking oil, but other fluids can be heated with this invention with minor modifications to the components.

The preferred material to comprise the heat transfer conduit 111 is black metallic composite, depending on the projected temperatures expected at the focus of the Fresnel lens 107. In alternate embodiments, using different liquids such as liquid metals and higher temperatures at the focus, metallic heat transfer conduits 107 would be required.

Experimental results obtained using a prototype of this invention show that even a small-scale apparatus can heat one gallon of water to boiling in less than 90 minutes. Temperatures much higher than 220 degrees Fahrenheit were achieved with a small model, and solid objects, such as a penny, were melted.

FIG. 3 and FIG. 4 display an alternate embodiment of the heat transfer conduit 120, which is comprised of a circular frame with a plurality of concentric heat transfer fins 121. The input 122 and output 123 to this conduit 120 are the same configuration as used in the preferred embodiment conduit 111.

The alternate embodiment conduit is comprised of a bottom layer 125, a gasket 126, and a sunside layer 127. The gasket 126 is placed between the bottom layer 125 and the sunside layer 127 to seal the conduit 120 and prevent leakage of the fluid to be heated. A plurality of bolts 130 are used to tighten down the removable bottom layer 125 onto the gasket 126 and the sunside layer 127.

Although the invention has been described as a preferred embodiment, equivalent features may be employed and substitutions made within this specification without departing from the scope of the invention as recited in the claims. 

1-4. (canceled)
 5. A system for heating a fluid which comprises: a support frame; a lens fixedly mounted on the support frame for concentrating solar radiation, and for directing the concentrated solar radiation onto a beam path; a heat transfer conduit fixedly mounted on the support frame at a pre-determined distance from the lens, wherein the heat transfer element is positioned on the beam path for receiving concentrated solar radiation from the lens to heat the heat transfer element; a motor assembly for moving the support frame, with the lens and heat transfer conduit thereon, to maintain a selected intensity of concentrated solar radiation incident on the heat transfer conduit; and a means for pumping fluid through the heat transfer conduit to heat the fluid.
 6. A system as recited in claim 5 wherein the heat transfer conduit comprises a body portion formed with a fluid passageway therethrough, and the system further comprises: a source of fluid to be heated; a fluid transfer input connecting the source of fluid in fluid communication with the passageway of the heat transfer conduit for moving fluid from the fluid source and into the heat transfer conduit; and a fluid transfer output connecting the heat transfer conduit in fluid communication with the source of fluid for moving fluid from the heat transfer conduit back to the fluid source.
 7. A system as recited in claim 6 wherein the heat transfer conduit is formed with a plurality of fluid passageways.
 8. A system as recited in claim 6 wherein the heat transfer conduit is made of a black metallic composite material.
 9. A system as recited in claim 6 wherein the fluid is selected from a group consisting of water and cooking oil.
 10. A system as recited in claim 5 wherein the motor assembly comprises: an altitude positioning motor connected with the support frame to establish an elevation angle for the beam path; an azimuth positioning motor connected with the support frame to establish an azimuth angle for the beam path; and a controller for coordinating operation of the altitude positioning motor with operation of the azimuth positioning motor to maintain a substantial alignment of the beam path with a direction from the system toward the sun.
 11. A system as recited in claim 10 further comprising: a sensor mounted on the support frame, wherein the sensor generates a signal indicative of the intensity of solar radiation incident on the sensor; and a means for electronically connecting the sensor to the controller for use by the controller in coordinating the respective operations of the altitude positioning motor and the azimuth positioning motor.
 12. A system as recited in claim 5 wherein the lens is a Fresnel lens.
 13. A system as recited in claim 5 further comprising: a means for selectively establishing the pre-determined distance on the support frame between the lens and the heat transfer conduit; and a means for selectively replacing lenses on the support frame.
 14. A system for heating a fluid which comprises: a lens for concentrating solar energy, and for directing the concentrated solar energy along a beam path; a heat transfer conduit positioned relative to the lens, at a fixed position on the beam path, to receive concentrated solar energy from the lens; a means for moving the heat transfer conduit in concert with the lens to maintain a selected intensity of solar radiation incident on the heat transfer conduit; and a means for pumping fluid through the heat transfer conduit to heat the fluid.
 15. A system as recited in claim 14 further comprising a support frame with the heat transfer conduit mounted on the support frame, and with the lens mounted on the support frame at a pre-determined distance from the heat transfer conduit to establish the beam path.
 16. A system as recited in claim 15 wherein the moving means comprises: an altitude positioning motor connected with the support frame to establish an elevation angle for the beam path; an azimuth positioning motor connected with the support frame to establish an azimuth angle for the beam path; and a controller for coordinating operation of the altitude positioning motor with operation of the azimuth positioning motor to maintain a substantial alignment of the beam path with a direction from the system toward the sun.
 17. A system as recited in claim 16 further comprising: a sensor mounted on the support frame, wherein the sensor generates a signal indicative of the intensity of solar radiation incident on the sensor; and a means for electronically connecting the sensor to the controller for use by the controller in coordinating the respective operations of the altitude positioning motor and the azimuth positioning motor.
 18. A system as recited in claim 14 wherein the heat transfer conduit comprises a body portion formed with a fluid passageway therethrough, and the system further comprises: a source of fluid to be heated; a fluid transfer input connecting the source of fluid in fluid communication with the passageway of the heat transfer conduit for moving fluid from the fluid source and into the heat transfer conduit; and a fluid transfer output connecting the heat transfer conduit in fluid communication with the source of fluid for moving fluid from the heat transfer conduit back to the fluid source.
 19. A system as recited in claim 14 wherein the lens is a Fresnel lens.
 20. A system as recited in claim 14 wherein the heat transfer conduit is made of a black metallic composite material.
 21. A method for heating a fluid which comprises the steps of: mounting a lens and a heat transfer conduit on a support frame with a pre-determined, straight-line distance, measured from the lens to the heat transfer conduit, to establish a beam path between the lens and the heat transfer conduit; directing solar energy, concentrated by the lens, along the beam path for incidence on the heat transfer conduit; moving the support frame, with the lens and heat transfer conduit thereon, to maintain a selected intensity of concentrated solar radiation incident on the heat transfer conduit; and pumping fluid through the heat transfer conduit to heat the fluid.
 22. A method as recited in claim 21 further comprising the steps of: elevating the support frame to establish an elevation angle for the beam path; turning the support frame to establish an azimuth angle for the beam path; and coordinating the elevating step with the turning step to maintain a substantial alignment of the beam path with a direction from the system toward the sun.
 23. A method as recited in claim 22 wherein the coordinating step is accomplished in response to the intensity of solar radiation incident on a sensor.
 24. A method as recited in claim 23 further comprising the steps of: selectively replacing lenses on the support frame; and selectively establishing the pre-determined distance between the lens and the heat transfer conduit. 